We (DH and I) live in NC and have been going to Myrtle Beach since we were kids! We have stayed all along the NC/SC coast, but I think our most memorable trip was the one last year in Surfside Beach, which is just south of Myrtle. Still close to everything in Myrtle, but without the overcrowded beaches/ammenities.
We did rent a house on VRBO (our second time going this route). It was wonderful! It was in a gated community and even had a golf cart for us to use. Now we did pay more than $1500, but I know there are lots of condos and houses on there to pick from. Just make sure you talk with the person who owns the property and also make sure they have a contract outlining all of the details and responsibilites. We had no problems at all!
I do disagree with the PP that said to stay out of North MB. We have stayed there often and even in Cherry Grove. It is really what you want out of your vacation. If you like to be in the "action" then staying right in MB might be best for you, but if you want to relax a little, stay in one of the smaller towns (Surfside Beach, Cherry Grove, NMB) they all have something to offer and are not far from MB.